Machines for producing letter envelopes, mailing wallets and similar products from paper and/or plastic webs operate continuously over several hours during a work shift. At the output end of the production machine, the products are counted and packaged into containers, especially into cartons, and the filled containers are either individually conveyed further or stacked on pallets. This packaging is still carried out by hand on many production machines. Because of continuous operation, two persons are usually required as packers at the reception point, so that they can substitute for one another as required. While one of these two persons works at the packaging table, the other person can, if need be, perform auxiliary services.
There exists an automatic packaging machine for the mechanical packaging of letter envelopes or mailing wallets. This is set up at the end of the respective production machine, immediately after the fan disks of the production machine. In this automatic packaging machine, the articles for packaging, in the form of letter envelopes or mailing wallets, are delivered by the fan disks, via a baffle plate, to two delivery belts which are arranged parallel to one another. The delivery belts are each guided round a belt pulley on two parallel shafts, of which one shaft is driven. A stack support is arranged above the plane of the delivery belts and is guided movably in the longitudinal direction of the delivery belts by means of a longitudinal guide. The individual articles of the packaging batch are laid down against the stack support by the fan disks of the production machine. This stack support is moved away from the fan disks, together with the packaging batch, by means of a drive.
In the region of the fan disks, there is a separating device or parting device, by means of which a stack comprising a specific number of individual articles of the packaging batch can be separated from the following packaging batch, while at the same time a gap is formed between the stack and the following packaging batch. This separating device has a separating fork which, in the region of the fan disks, rises from below the resting plane of the delivery belts into the gap between two individual articles still located in the slots of the fan disk and which thereby makes separation possible. This separating fork is guided parallel to itself by means of a parallel crank mechanism and is moved on a circular path, with the result that, over a short distance, it moves together with the packaging batch.
Because the separating fork is arranged in the region of the fan disks, so that it can engage into the interspace between two individual articles of the packaging batch which are still kept separate from one another in the slots of the fan disk, and because, owing to its circular path of movement, it can travel only a limited distance together with the individual articles, only a relatively small number of individual articles can be picked up between it and the fan disks. Thus, the stack separated by the separating fork has to be brought out of the path of movement of the following packaging batch as quickly as possible, to ensure that the stack support can thereupon be brought once again into its supporting position in front of the end face of the following packaging batch. This is necessary so that it can take over the job of supporting the packaging batch well before the separating fork has withdrawn too far. To move away the stack, there is a transfer arrangement which is arranged above the delivery belts. It grasps the stack separated from the following packaging batch and brings it into a transfer position, where the stack is pushed out downwardly into an opened carton.
The transfer arrangement has two transport forks which are arranged on a slide in succession in the direction of the conveying movement of the packaging batch. One transport fork is arranged rigidly on the end of the slide in the direction of movement of the packaging batch. The second transport fork is connected to the slide by means of a vertical lifting device. This is guided movably relative to the first transport fork on a horizontal longitudinal guide of the slide and is coupled to a drive. The slide of the transfer arrangement is itself guided on horizontal longitudinal guides so as to be moveable from the take-over point to the transfer point. It is moved to and from between the takeover point and the transfer point by means of a chain drive.
The stack is grasped by the transfer arrangement according to a procedure in which the stack support, after reaching the rigid transport fork, is retracted laterally out of the path of movement of the stack, with the result that the stack comes up against the rigid transport fork. The stack support is moved back into its initial position in the vicinity of the fan disks. The moveable transport fork is lowered into the gap between the stack and the packaging batch by means of the lifting device and is moved toward the rigid transport fork a certain amount by means of the horizontal drive. The stack located between the two transport forks is thereby compressed and clamped between the transport forks. In this state, the stack is conveyed by the transfer arrangement toward the filling station.
The stack support is once again pushed transversely into the path of movement of the following stacking batch by being inserted into the larger gap produced when the stack is compressed between the moveable transport fork and the separating fork.
In the filling station, the stack held by the transport forks partially rests on bottom plates which are shorter than the stack length. These bottom plates can each be slung down about a pivot axis aligned horizontally and at the same time transversely relative to the path of movement of the stack, from the horizontal position into a position directed vertically downwardly. As a container, a carton with an opened flap is generally raised from below into the filling station. The bottom plates are then swung downwardly into the carton, so that they can serve as guides for the stack. The stack, still held constantly by the transport forks, is pressed out of the transport forks downwardly into the carton by a vertically guided and driven rake. The transfer arrangement with the two transport forks then moves back to the take-over position again. The moveable transport fork is previously raised, so that it can be guided over and beyond the newly formed stack. As soon as the gap is formed at the end of the next stack, the moveable transport fork is lowered into this gap, and this is followed by the next work cycle.
In this transfer arrangement, it is very difficult to change over to other formats. This is also true of a change-over when the paper thickness is changed and/or when the number of articles in a stack is changed. The separating fork in the region of the fan disks has a stroke of only finite length, and because of this it can also only enter a stack from below up to a specific height. If the stack is of greater height, it can happen that the top edges of the last individual articles of the stack and of the first individual articles of the following packaging batch tip over into the gap, thus impeding, if not even preventing the lowering of the moveable transport fork. This transfer arrangement is therefore suitable only for letter envelopes or mailing wallets of limited height. Moreover, if the height of the stack is changed, the stroke of the pushing-in rake and the stroke of the carton-lifting device must be altered.
Furthermore, whenever the format width is changed, at least the two outer fork prongs of both transport forks have to be set exactly to the new format width. The standing position of the carton must be set to the format width. Whenever the stack length is changed, both the forward movement and the reverse movement of the stack support must be adjusted accordingly. Furthermore, the distance of the two transport forks from one another and in relation to the degree of compression has to be adjusted, the latter depending not only on the stack length but also on the paper thickness, the paper quality and the make-up of the letter envelopes or mailing wallets. Moreover, the carton also has to be set to the changed stack length, inasmuch as the travel of the transport forks remains the same, specifically in relation to the moveable transport forks.
Insofar as the pivot axis of the bottom plates in the filling station is aligned parallel to the direction of movement of the stack, if there is a relatively large variation in the stack length the bottom plates have to be exchanged, because they cannot, of themselves, be either lengthened or shortened. The same applies in a similar way to a variation in the format width, insofar as the pivot axes of the bottom plates are aligned transversely relative to the direction of movement of the stack. Either several groups of bottom plates must be provided for this, or the variation in format is sharply restricted.
In view of the numerous adjusting operations which are necessary, such an automatic packaging machine is very cumbersome where the change-over to other formats is concerned. It can therefore be used to only a limited extent, especially when the batch sizes are relatively small.
A serious disadvantage of this automatic packaging machine is also that the stack is clamped in the filling station between the two transport forks as a free carrier, specifically at the latest from the moment when the bottom plates were swung away downwardly. In such a stack, those surface regions which, because of the larger number of paper layers resting on top of one another, can most easily absorb the compressive forces of the two transport forks in the stack, are distributed in a widely varying manner over the end face of the stack. Consequently, the phenomena of the buckling column with an off-center load or, expressed in the opposite way, with a central load and a cross-section with off-center load bearing occur here. In most cases, that surface region of the stack which transmits the compressive force of the transport forks is at the bottom, and the upper surface regions cannot contribute to supporting the internal bending moment because of the smaller number of their paper layers. Such a carrier clamped only at the two ends all too easily breaks in the middle under its own weight. It can therefore happen that, at the moment when the bottom flaps have been swung downwardly into the carton, the carrier comprising the individual articles sags downwardly in the middle and, after only slight sagging, suddenly breaks open downwardly, specifically even before it has been possible for the lateral edges of the stack to be pushed downwardly by the rake. At best, such a stack which has broken open can be re-arranged by laborious manual work and forced into the carton, by equally laborious manual work. Even when only one fault of this kind occurs, the entire production machine has to be stopped until the damage is rectified. Such an automatic packaging machine therefore puts the smooth operation of the production machine at great risk. Such faults are all the more to be expected because the paper quality of the letter envelopes or mailing wallets, especially as regards the stiffness of the paper as such, the stiffness of the folding point and the flexibility of the paper over its surface and particularly at the folding edges, can vary very widely. There are also great differences as regards the surface roughness on the outer face of the letter envelopes or mailing wallets.